Jacks and jack assemblies have long been used with towed vehicles. Typically, a jack assembly is secured to a towed trailer such as a straight tongue or an A-frame type trailer and assists in stabilizing the towed trailer while the trailer is detached from a towing vehicle. In addition, a jack assembly often assists in engaging a towed vehicle with a towing vehicle or disengaging a towing trailer from a towing vehicle. A jack assembly may be utilized to maintain a towed vehicle in a level position when the towed vehicle is disengaged from a towing vehicle. A jack assembly may also be utilized to change the vertical position or height of the tongue of a trailer as the tongue is mounted onto or dismounted from the hitch of a towing vehicle.
Such jack assemblies are commonly pivotally mounted onto the trailer tongue so as to be pivotally moveable between a vertical position and a horizontal position. The horizontal position often allows the jack assembly to be stowed when the jack assembly is not in use. Most conventional jack assemblies are manually toggled between a raised position and a lowered position by the use of a crank and gear assembly. These jack assemblies utilize rotation that is translated into linear motion to extend or retract a portion of the jack assembly.
Additionally, other jack assemblies are automatically powered by an electric motor device. The rotation of the rotor ultimately rotates a screw that translates a nut thereon. The nut may be attached to a jack leg and extends or retracts the jack leg from the jack body. The direction that the screw is rotated toggles the direction that the jack leg linearly translates relative to the jack body. However, electric powered jack assemblies have power limitations due to the friction caused by the interaction of the rotor, gears, screw, and nut. This friction causes significant heat and energy loss thereby restricting the overall load that is capable of being lifted and supported on the jack assembly.
In some instances, high powered jacks are capable of supporting and translating increased loads at a particular rate of speed. However, these high powered jacks utilize an electrical system that utilizes an electric motor, to operate a hydraulic pump or compressor as well as an assembly that automatically toggles a solenoid valve to pressurize a hydraulic or pneumatic system to cause the jack leg to linearly translate relative to the jack body. These high powered jacks require electrical, hydraulic or pneumatic, and mechanical systems working together to properly operate and support a heavy load, for example, loads in excess of 8,000 lbs. These systems require a plurality of different types of mechanisms, may be costly to manufacture, and, due to an increased number of movable parts, may have a higher risk of failure. Further, the energy conversion from electrical to hydraulic to mechanical may include an unavoidable energy loss that is irreversible. This phenomenon will increase entropy which is evidence of the inefficiencies.
In further instances, high powered jacks configured to translate a heavy load are susceptible to overload protection requirements as well as braking requirements to control the translation of the jack. For example, overload protection may include an over-current protector used as a torque limiting mechanism. During an overload situation, the current increases when the load increases. An over-current protector would allow the power source to be disconnected when over-current occurs, effectively limiting the torque and prevent breakdown of the transmission mechanism.
The jack would also include a brake device to stop translation while maintaining the heavy load in position thereon. However, the prior art high powered jacks have failed to provide both overload protection and brake requirements in a sufficient manner that would support the heavy load functionality of the jack. Due to multiple types of energy conversions, jack designs should provide a brake device to stop translation considering each energy form (electric, pneumatic, hydraulic) beginning at the electric motor and continuing down the power path through each of the multiple iterations of energy conversion to the final method of elevation of the heavy load. Therefore, the brake device must also account for all types of system failures (ie. if a hydraulic or pneumatic tube or valve breaks) in order to maintain the load.
For example, known prior art high powered jacks may incorporate a brake device such as a conventional electromagnetic brake used as a brake mechanism wherein the electromagnetic brake and the overload protection mechanism are installed at different positions of the jack. Such an arrangement increases the cost of manufacturing and further may not be compatible for smooth jack operation. This arrangement may subject the internal mechanisms to an increase risk of cyclic failure over time. Further, these mechanisms require a power supply and, may be particularly suspect during low voltage conditions such as high current startup. Thus, the power jack may be inoperable in situations of low battery or insufficient voltages. Additionally, the overload protection mechanism and brake device may require some buffer time for shutdown and startup which may be undesirable.
Therefore there is a need for a high powered jack assembly that is not subject to significant friction and energy loss. There is also a need for providing a high powered jack assembly that does not rely on hydraulic or pneumatic systems to support a heavy load and lift a load at an increased rate of speed. Additionally, there is a need for overcoming the drawbacks of the prior art.